Pregnant women with low 25-hydroxyvitamin D levels may be more likely to have children who develop language difficulties, an Australian study showed.

Action Points

Explain that pregnant women with low 25-hydroxyvitamin D levels may be more likely to have children who develop language difficulties.

Note that there was no relationship between maternal serum 25(OH)D levels and behavioral or emotional problems in the children.

Pregnant women with low 25-hydroxyvitamin D levels may be more likely to have children who develop language difficulties, an Australian study showed.

Children born to mothers with 25(OH)D levels less than 46 nmol/L in the second trimester were nearly twice as likely to have clinically significant language problems at ages 5 and 10 (OR 1.97, P<0.05), according to Andrew Whitehouse, PhD, of the University of Western Australia's Telethon Institute for Child Health Research in Subiaco, and colleagues.

There was no relationship, however, between maternal serum 25(OH)D levels and behavioral or emotional problems in the children, the researchers reported online in Pediatrics.

"The findings suggest that the trend over the past decade of a reduction in vitamin D levels among women of reproductive age has significant implications for offspring neurodevelopment and public health more generally," they wrote.

"Randomized controlled trials of vitamin D supplementation are required to verify these observational data that suggest that an adequate maternal vitamin D status during pregnancy is necessary for optimal language development in offspring."

A previous study identified an association between the timing of pregnancy and the risk of multiple sclerosis, with a greater risk in pregnancies that started in the winter or spring, when sunlight exposure and vitamin D levels are at their lowest.

That suggested that vitamin D insufficiency may be to blame for various adverse health outcomes, including possibly impaired neurocognitive development.

Whitehouse and colleagues explored the issue using data from the Western Australian Pregnancy Cohort (Raine) Study conducted in Perth. The current analysis included 743 white women who provided blood samples at 18 weeks of pregnancy, a key time for fetal neurodevelopment.

The researchers divided the women into quartiles according to their serum 25(OH)D levels:

46 nmol/L or less

47 to 59 nmol/L

60 to 71 nmol/L

72 nmol/L or more

Offspring behaviors were assessed at ages 2, 5, 8, 10, 14, and 17 using the Child Behavior Checklist. There was no association between maternal serum 25(OH)D and behavioral outcomes at any age.

There was, however, an association between the lowest 25(OH)D levels (versus the highest) and a greater percentage of children with clinically significant impairments in receptive language, measured using the Peabody Picture Vocabulary Test-Revised at ages 5 and 10.

The authors used generalized estimating equations models to show the association between maternal 25(OH)D concentration at 18-weeks pregnancy and offspring language impairment during childhood. In a model that adjusted for maternal age at conception, family income, maternal smoking during pregnancy, offspring parity, and the season of maternal blood collection, they found the following:

46 nmol/L or less: OR 1.97 (95% CI 1.00–3.93), P<0.05

47 to 59 nmol/L: OR 1.35 (95% 0.71–2.57), P=0.36

60 to 71 nmol/L: OR 1.44 (95% CI 0.74–2.80), P=0.28

72 nmol/L or more: OR 1.00 (reference), no P-value

The relationship remained significant after adjustment for all the factors, "indicating that the association was primarily driven by maternal [25(OH)D] levels, rather than other seasonal factors," according to the researchers.

Although an observational study cannot prove a causal relationship, there is a biological connection between maternal vitamin D and the developing fetus. Vitamin D has important functions during neurodevelopment, "including a signaling role in neuronal differentiation, a regulation role in the metabolism of neurotrophic factors and neurotoxins, and a protective role during brain inflammation," Whitehouse and colleagues wrote.

They added that vitamin D may also be involved indirectly in fetal brain growth.

The study was limited, they said, by sample attrition over time and the inclusion of only Caucasian participants.

The study was supported by the National Health and Medical Research Council (NHMRC) and the Telethon Institute for Child Health Research (TICHR) by long-term contribution to funding this study over the past 20 years. Core Management of the Raine study is funded by the University of Western Australia (UWA); Curtin University; the UWA Faculty of Medicine, Dentistry, and Health Sciences; the Raine Medical Research Foundation; TICHR; and the Women and Infants Research Foundation.

Whitehouse is funded by a Career Development Fellowship from the NHMRC and one of his co-authors is supported by a Principal Research Fellowship from the NHMRC.